An indazol-3-ylmethyl triphenyl phosphonium salt [Compound (IVb)] represented by Formula (IVb):
(wherein Ph represents phenyl, Xb represents each atom of chlorine, bromine, or iodine) is known as useful synthetic intermediate of indazole derivative which is useful as an anti-tumor agent or a protein kinase inhibitor (refer to Patent Document 1 and Patent Document 2).
According to the said gazettes, Compound (IVb) can be produced from commercially available indazol-3-carboxylic acid by 4 steps in a similar manner to methods described in Nonpatent Document 1 or Nonpatent Document 2. However, these methods require number of steps and ate not suitable for industrial mass production. Therefore, simpler and more efficient producing method of indazol-3-ylmethyl phosphonium salt is desired.    Patent Document 1: WO2005/012257    Patent Document 2: WO2005/012258    Nonpatent Document 1: Journal of Organic Chemistry, 1987, vol. 52, p. 19    Nonpatent Document 2: Canadian Journal of Chemistry, 1973, vol. 51, p. 792